Convert timedelta to total seconds

I have a time difference

import time
import datetime

time1 = datetime.datetime.fromtimestamp(time.mktime(time.gmtime()))
...
time2 = datetime.datetime.fromtimestamp(time.mktime(time.gmtime()))
diff = time2 - time1

Now, how do I find the total number of seconds that passed? diff.seconds doesn’t count days. I could do:

diff.seconds + diff.days * 24 * 3600

Is there a builtin method for this?